Self-adjusting seal for rotating turbomachinery

ABSTRACT

A self-adjusting seal has a movable seal member fitted in a groove of a dummy ring along a rotor. The movable seal member is biased outwardly in a radial direction by a disc spring, and a gap between the movable seal member and the rotor is large during the start-up or shutdown of rotating turbomachinery. On the other hand, during a rated operation of the rotating turbomachinery, by a fluid having flown into the internal portion of the groove via a gap between a high pressure side end surface of the movable seal member and the groove, the movable seal member is pressed toward the rotor against a biasing force of the disc spring.

TECHNICAL FIELD

The present invention relates to a self-adjusting seal used in rotating turbomachinery such as, for example, a steam turbine, a gas turbine and a compressor. Herein, the self-adjusting seal denotes a seal in which a seal gap is automatically adjusted in accordance with the operational state of the rotating turbomachinery.

BACKGROUND ART

In rotating turbomachinery such as a steam turbine, a gas turbine and a compressor, in terms of an improvement in operation efficiency, a seal for preventing the leakage of a working fluid via a gap between a rotational member (a rotor or a blade) and a stationary member (a casing or a vane) is provided at various positions.

Examples of the seal include a dummy ring seal provided between a high pressure portion and an intermediate pressure portion of a high/intermediate pressure integrated type steam turbine, a ground seal provided at a portion where a rotor extends through a casing, a blade tip seal provided between the tip of a blade and the casing, and a vane tip seal provided between the tip of a vane and the rotor.

As the seal of this type, conventionally, a labyrinth seal composed of a labyrinth block having a plurality of fins and a plate spring for elastically supporting the labyrinth block from its back surface side has been typically used. In this case, the labyrinth block is held from the back surface side by the plate spring in a state where the labyrinth block is fitted in a groove formed in a stationary member, and the gap between the fins and a rotational member is kept constant. With this, when passing through the minute gap between the fins and the rotational member, a fluid sharply expands and the pressure is reduced so that the leakage of the fluid is prevented.

However, in the labyrinth seal having the above-described configuration, when the gap between the fins and the rotational member is extremely small, depending on the operational state of the rotating turbomachinery (particularly during the start-up or shutdown), there have been cases where the fins comes in contact with the rotational member due to the influence resulting from a difference in thermal expansion between the rotational member and the stationary member, and the abrasion of the fins and a shaft vibration are generated. On the other hand, when the gap between the fins and the rotational member is increased, there has been a problem that the leakage of the fluid cannot be sufficiently prevented so that the operation efficiency of the rotating turbomachinery is reduced.

To cope with this, as a seal replacing the conventional labyrinth seal, Patent Document 1 describes a self-adjusting seal in which the seal gap is automatically adjusted in accordance with the operational state of the rotating turbomachinery.

The seal is composed of a stationary seal ring disposed close to a horizontal dividing plane of a rotational member (a rotor) and a movable seal ring disposed close to the center. Of the members, the movable seal ring is biased outwardly in a radial direction by an elastic body (a corrugated plate spring, disc spring, metal bellows, and the like) so that the seal gap during the start-up or shutdown of the rotating turbomachinery is sufficiently secured. On the other hand, during a rated operation of the rotating turbomachinery, the movable seal ring is pressed inwardly in the radial direction against a biasing force of the elastic body by the pressure of a fluid in the rotating turbomachinery so that the seal gap can be minimized.

-   [Patent Document 1] Japanese Patent Application Laid-open No.     2000-97352

In consideration of a frictional force (f) of a relative sliding portion between the movable seal ring and a stationary member to which the movable seal ring is fixed, the self-adjusting seal described in Patent Document 1 is designed such that a fluid pressure (P) applied to the back surface of the movable seal ring is sufficiently larger than the biasing force (F) by the elastic body.

That is, the shape (an effective area) of the movable seal ring and the material and shape of the elastic body are determined such that the following inequality (1) is satisfied during the rated operation of the rotating turbomachinery:

back surface pressure (P)×seal ring effective area (A)>biasing force (F)+frictional force (f)   (1).

However, in reality, the self-adjusting seal designed by such method does not necessarily work properly, and there is a possibility that the seal gap during the rated operation of the rotating turbomachinery becomes excessively large so that the leakage of the fluid cannot be sufficiently prevented, or that, by contrast, the movable seal ring operates before the rotating turbomachinery passes a critical point during an unsteady operation of the rotating turbomachinery, and the movable seal ring comes in contact with the rotational member. In particular, when the latter situation occurs in an ACC abradable seal which has been actively developed in recent years, damage beyond expectation is caused to an abradable material provided on the surface of the movable seal ring, and a desired seal gap cannot be formed thereafter. Note that the ACC abradable seal mentioned herein denotes a self-adjusting seal in which the abradable material, which can be easily cut, is provided on the surface of the movable seal ring such that heat generation resulting in a bending deformation of the rotational member is suppressed even when the movable seal ring is brought into contact with the rotational member from any cause.

In addition, when a plurality of self-adjusting seals are arranged as a dummy ring seal, there are cases where timing at which the movable seal ring operates varies.

To cope with this, as the result of elaborate studies on a factor which influences the operation of the self-adjusting seal by the present inventors, there has been obtained knowledge that the frictional force (f) of the relative sliding portion between the movable seal ring and the stationary member greatly varies due to the individual difference of the self-adjusting seal, and significantly influences the operation of the self-adjusting seal.

SUMMARY OF INVENTION

The present invention has been achieved in view of the above-described circumstances, and an object thereof is to provide a self-adjusting seal which operates at desired timing in accordance with the operational state of the rotating turbomachinery, and is capable of properly adjusting the seal gap.

The self-adjusting seal for rotating turbomachinery according to the present invention is a self-adjusting seal for rotating turbomachinery in which a rotational member rotates while confronting a stationary member and energy transfer between the rotational member and a fluid is performed, including a movable seal member fitted in a groove provided in the stationary member along the rotational member, and a biasing member biasing the movable seal member so as to increase a gap between the rotational member and the movable seal member, wherein at least during a rated operation of the rotating turbomachinery, the movable seal member is pressed toward the rotational member against a biasing force of the biasing member by the fluid having flown into an internal portion of the groove via a gap between a high pressure side end surface of the movable seal member and the groove, and at least one of a low pressure side end surface of the movable seal member and a wall surface of the groove opposing the low pressure side end surface is subjected to a process for facilitating relative sliding between the low pressure side end surface of the movable seal member and the wall surface of the groove.

In the present specification, the process for facilitating relative sliding denotes any process for reducing a friction coefficient in a relative sliding portion. Note that, although the friction coefficient in the relative sliding portion differs depending on materials for the movable seal member and the stationary member and the like, when a special process is not performed, the friction coefficient is normally more than 0.5. Therefore, the process for facilitating relative sliding can be defined as a process for setting the friction coefficient in the relative sliding portion to not more than 0.5, and means a process for setting the friction coefficient in the relative sliding portion to, e.g., 0.1 to 0.5.

In the above-described self-adjusting seal, at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove of the stationary member opposing the low pressure side end surface (i.e., the relative sliding portion between the movable seal member and the stationary member) is subjected to the process for facilitating the relative sliding therebetween. As a result, frictional force (f) of the second term on the right side of the above-described inequality (1) is reduced, and the operation timing of the self-adjusting seal is determined mainly by the magnitude relation between back surface pressure (P)×seal ring effective area (A) on the left side and biasing force (F) of the first term on the right side. With this, the frictional force of the relative sliding portion which tends to vary due to the individual difference of the self-adjusting seal does not significantly influence the operation of the self-adjusting seal, and hence it is possible to cause the self-adjusting seal to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

In addition, the relative sliding portion between the movable seal member and the stationary member is subjected to the process for facilitating the relative sliding, whereby variations in the frictional force of the relative sliding portion themselves are reduced, and hence it is possible to cause the self-adjusting seal to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

In the above-described self-adjusting seal for rotating turbomachinery, as the process for facilitating the relative sliding, a lubricating coating may be formed on at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface.

In this case, the lubricating coating can be formed by, e.g., application, thermal spraying, or plating.

In addition, the lubricating coating may contain a solid lubricant made of at least one of molybdenum disulfide, graphite, tungsten disulfide, graphite fluoride, boron nitride, copper, nickel, lead, tin, silver, tetrafluoroethylene, polyimide, and high density polyethylene.

When the lubricating coating containing the solid lubricant is used, a dimple for fixing the solid lubricant is preferably formed on at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface.

With this, it is possible to prevent the loss of the effect of facilitating the relative sliding between the movable seal member and the groove wall surface of the stationary member, and maintain the normal operation of the self-adjusting seal for a long period of time.

In the above-described self-adjusting seal for rotating turbomachinery, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member may be chamfered.

Alternatively, in the above-described self-adjusting seal for rotating turbomachinery, as the process for facilitating the relative sliding, a surface roughness Ra of at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface may be set to not more than 6.3 μm.

In the above-described self-adjusting seal for rotating turbomachinery, a coating made of an abradable material is preferably formed on a surface of the movable seal member opposing the rotational member.

In the self-adjusting seal having the abradable material provided on the surface of the movable seal member in this manner (what is called an ACC abradable seal), even when the movable seal member is brought into contact with the rotational member from any cause during the operation of the rotating turbomachinery, the abradable material is easily cut so that it is possible to suppress heat generation and prevent a bending deformation of the rotational member resulting from the heat generation. Consequently, the commercialization thereof is in strong demand. However, in the case of the ACC abradable seal, when the movable seal member operates before desired timing so that the seal gap is reduced before the rotating turbomachinery reaches the rated operation (particularly before passing a critical point during an unsteady operation) and the movable seal member comes in contact with the rotational member, damage beyond expectation is caused to the abradable material, and a desired seal gap cannot be formed thereafter.

In this regard, since the above-described self-adjusting seal can operate at desired timing in accordance with the operational state of the rotating turbomachinery, when the self-adjusting seal is applied to the ACC abradable seal, it is possible to prevent the damage beyond expectation to the abradable material.

According to the present invention, since the relative sliding portion between the movable seal member and the stationary member is subjected to the process for facilitating the relative sliding therebetween, the operation timing of the self-adjusting seal is determined mainly by the relation between the biasing force by the biasing member and the pressure of the fluid pressing the movable seal member toward the rotational member against the biasing force. Consequently, the frictional force of the relative sliding portion which tends to vary due to the individual difference of the self-adjusting seal does not significantly influence the operation of the self-adjusting seal, and hence it is possible to cause the self-adjusting seal to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

In addition, the relative sliding portion between the movable seal member and the stationary member is subjected to the process for facilitating the relative sliding, whereby variations in the frictional force of the relative sliding portion themselves are reduced, and hence it is possible to cause the self-adjusting seal to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing an example of an entire configuration of a self-adjusting seal;

FIG. 2 is a cross-sectional view showing an example of a configuration of a movable seal member;

FIG. 3 is a view schematically showing the movement of the movable seal member in accordance with an operational state of rotating turbomachinery in which FIG. 3( a) shows the state of the movable seal member during the start-up or shutdown, while FIG. 3( b) shows the state of the movable seal member during a rated operation;

FIG. 4 is a cross-sectional view showing an example of a configuration of a movable seal member in a self-adjusting seal of a first embodiment;

FIG. 5 is a cross-sectional view showing an example of a configuration of a movable seal member in a self-adjusting seal of a second embodiment;

FIG. 6 is a cross-sectional view showing an example of a configuration of a movable seal member in a self-adjusting seal of a third embodiment; and

FIG. 7 is a cross-sectional view showing an example of another configuration of the movable seal member.

DESCRIPTION OF EMBODIMENTS

A description is given hereinbelow of embodiments of the present invention with reference to the accompanying drawings. Note that the scope of the present invention is not limited to dimensions, materials, shapes, and relative arrangements of constituent parts described in the embodiments unless specifically described, and they are only explanatory examples.

First Embodiment

FIG. 1 is a front view showing an example of an entire configuration of a self-adjusting seal for rotating turbomachinery. As shown in the drawing, a self-adjusting seal 1 is composed of a stationary seal member 10 and a movable seal member 20 which are annularly provided along a rotor 2 of rotating turbomachinery.

The self-adjusting seal 1 is fitted in a groove formed in a dummy ring 4 (see FIG. 2) attached to a casing (not shown) of the rotating turbomachinery so as to seal a gap between the rotor 2 and the dummy ring 4. Although a description is given hereinbelow of an example in which the self-adjusting seal 1 is used as a dummy ring seal provided between the dummy ring 4 serving as a stationary member of the rotating turbomachinery and the rotor 2 serving as a rotational member, the self-adjusting seal according to the present invention can be used as various seals for the rotating turbomachinery including a ground seal, blade and vane tip seals, and the like.

The stationary seal member 10 has a pair of an upper member 10A and a lower member 10B provided on left and right sides of the rotor 2, and the upper and lower members 10A and 10B making the pair are joined to each other at joint surfaces 12. An inner periphery of the stationary seal member 10 is provided with seal fins, and the seal fins and an uneven groove formed along a circumferential direction of the rotor 2 create a labyrinth effect to prevent the leakage of a fluid (steam when the rotating turbomachinery is a steam turbine) via the gap between the stationary seal member 10 and the rotor 2.

The stationary seal member 10 is elastically supported from its back surface side by a plate spring or the like, and can move outwardly in a radial direction when the stationary seal member 10 comes in contact with the rotor 2. However, the stationary seal member 10 is basically immovable, and does not move in accordance with the operational state of the rotating turbomachinery.

On the other hand, as described later, the movable seal member 20 has a large seal gap between itself and the rotor 2 during the start-up or shutdown of the rotating turbomachinery, and, during a rated operation of the rotating turbomachinery, the movable seal member 20 moves in directions of arrows in the drawing so as to abut on the stationary seal member 10 at joint surfaces 14, whereby the seal gap is reduced.

FIG. 2 is a cross-sectional view showing an example of a configuration of the movable seal member 20. As shown in the drawing, the movable seal member 20 is fitted in a groove 6 formed in the dummy ring 4 attached to the casing.

An inner periphery of the movable seal member 20 is provided with seal fins 22, and an uneven groove 8 formed along the circumferential direction of the rotor 2 and the seal fins 22 create the labyrinth effect to prevent the leakage of the fluid via the gap between the movable seal member 20 and the rotor 2.

In addition, inside the groove 6 of the dummy ring 4, there are provided a disc spring 30 for biasing an upper holding plate 24 of the movable seal member 20 outwardly in the radial direction, and a support plate 32 for supporting the disc spring 30 from below. With this, the movable seal member 20 is biased by the disc spring 30 such that the gap between the seal fins 22 and the rotor 2 is increased. Note that any biasing member such as a plate spring or metal bellows may also be used instead of the disc spring 30.

FIG. 3 is a view schematically showing the movement of the movable seal member 20 in accordance with the operational state of the rotating turbomachinery in which FIG. 3( a) shows the state of the movable seal member 20 during the start-up or shutdown of the rotating turbomachinery, while FIG. 3( b) shows the state of the movable seal member 20 during the rated operation of the rotating turbomachinery.

As shown in FIG. 3( a), during the start-up or shutdown of the rotating turbomachinery, the movable seal member 20 is pushed up outwardly in the radial direction by a biasing force F of the disc spring 30, and the gap between the seal fins 22 and the rotor 2 is increased.

On the other hand, during the rated operation of the rotating turbomachinery, as shown in FIG. 3( b), a difference in the pressure of the fluid is generated between both sides of the movable seal member 20, the movable seal member 20 receives a thrust force (a force resulting from the pressure difference) F₀ to move toward a low pressure side (the right side of the movable seal member 20 in the example shown in the drawing), and a low pressure side end surface 26 of the movable seal member 20 comes in contact with a groove wall surface (a wall surface 9 of the groove 6 opposing the low pressure side end surface 26) of the dummy ring 4. At this point, the fluid on the high pressure side passes through the gap between a high pressure side end surface 28 of the movable seal member 20 and the groove 6 of the dummy ring 4, and flows into an internal space 7 of the groove 6 so that the pressure in the internal space 7 of the groove 6 rises (note that, though not shown, there are provided bypass grooves for guiding the fluid on the high pressure side to the internal space 7 of the groove 6 at several positions along the circumferential direction of the stationary seal member 20 in FIG. 1). As a result, the movable seal member 20 is pressed inwardly in the radial direction by the high pressure fluid having flown into the internal space 7 of the groove 6.

At this point, in order to actually cause the movable seal member 20 to move inwardly in the radial direction, the following inequality needs to be satisfied:

back surface pressure (P)×seal ring effective area (A)>biasing force (F)+frictional force (f)   (1).

Herein, the frictional force (f) is obtained by multiplying a friction coefficient μ₀ in a relative sliding portion 29 between the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 by the thrust force F₀.

As the result of elaborate studies, the present inventors have understood that the frictional force (f) of the relative sliding portion 29 tends to vary, and the frictional force (f) of the relative sliding portion 29 significantly influences the operation of the self-adjusting seal 1.

Consequently, in the present embodiment, a process for facilitating the relative sliding in the relative sliding portion 29 is performed by providing a lubricating coating on at least one of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26.

FIG. 4 is a cross-sectional view showing an example of a configuration of the movable seal member 20 having the lubricating coating provided in the relative sliding portion 29. In the example shown in the drawing, although a rubricating coating 40 is provided on both of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26, the lubricating coating 40 may also be provided only on one of them. Note that the thickness of the lubricating coating 40 is preferably in a range of 2 to 7 μm in terms of sufficient facilitation of the relative sliding in the relative sliding portion 29.

With regard to a method for forming the lubricating coating 40, an appropriate method is preferably selected in accordance with the material forming the lubricating coating 40, and application, thermal spraying, or plating may be selected as the method. For example, by applying a grease or paste in which a powdery or scaly solid lubricant having antifriction properties is dispersed, the lubricating coating 40 may be formed.

The solid lubricant used in the lubricating coating 40 is preferably made of at least one of molybdenum disulfide, graphite, tungsten disulfide, graphite fluoride, boron nitride, copper, nickel, lead, tin, silver, tetrafluoroethylene, polyimide, and high density polyethylene. Among them, molybdenum disulfide excellent in lubricating and heat resistance properties can be suitably used as the material for the lubricating coating 40.

When the lubricating coating 40 contains the solid lubricant, it is preferable to provide a dimple 42 on one of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26 to fix the solid lubricant. Note that FIG. 4 shows an example in which the dimple 42 is provided on the wall surface 9 of the groove 6 opposing the low pressure side end surface 26.

With this, it is possible to prevent the loss of the effect of facilitating the relative sliding between the movable seal member 20 and the wall surface of the groove 6, and maintain the normal operation of the self-adjusting seal 1 for a long period of time.

The dimple 42 may also be formed as a concave portion having a depth of about 10 μm by, e.g., shot peening.

Second Embodiment

Next, a description is given of a self-adjusting seal of a second embodiment.

The self-adjusting seal of the present embodiment is the same as the self-adjusting seal of the first embodiment except for the specific implementation of the process for facilitating the relative sliding in the relative sliding portion 29 between the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26. Accordingly, a description is given herein only of the process for facilitating the relative sliding in the relative sliding portion 29.

FIG. 5 is a cross-sectional view showing an example of a configuration of the portion in the vicinity of the low pressure side end surface 26 of the movable seal member 20 in the self-adjusting seal of the present embodiment. As shown in the drawing, as the process for facilitating the relative sliding in the relative sliding portion 29, corners 44 of the wall surface 9 of the groove 6 opposing the low pressure side end surface 26 of the movable seal member 20 are chamfered (preferably chamfering of not less than 1 mm). By chamfering each corner 44, it is possible to prevent the corner 44 from being caught on the low pressure side end surface 26 of the movable seal member 20, and facilitate the relative sliding in the relative sliding portion 29.

Note that, although the shape of the corner 44 after the chamfering is not particularly limited, as shown in FIG. 5, by forming the corner 44 into an R shape (a curved shape), it is possible to reliably prevent the corner 44 from being caught on the low pressure side end surface 26 of the movable seal member 20.

Third Embodiment

Subsequently, a description is given of a self-adjusting seal of a third embodiment.

The self-adjusting seal of the present embodiment is the same as the self-adjusting seal of the first embodiment except for the specific implementation of the process for facilitating the relative sliding in the relative sliding portion 29 between the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26. Accordingly, a description is given herein only of the process for facilitating the relative sliding in the relative sliding portion 29.

FIG. 6 is a cross-sectional view showing an example of a configuration of the portion in the vicinity of the low pressure side end surface 26 of the movable seal member 20 in the self-adjusting seal of the present embodiment. In the present embodiment, a surface roughness Ra of at least one of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26 is set to not more than 6.3 μm. With this, it is possible to reduce the friction coefficient μ₀ in the relative sliding portion 29, and facilitate the relative sliding in the relative sliding portion 29.

As has been described above, in each of the first to third embodiments, at least one of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26 is subjected to some process for facilitating the relative sliding therebetween. As a result, frictional force (f) of the second term on the right side of the above-described inequality (1) is reduced, and the operation timing of the self-adjusting seal 1 is determined mainly by the magnitude relation between back surface pressure (P)×seal ring effective area (A) on the left side and biasing force (F) of the first term on the right side. With this, the frictional force of the relative sliding portion 29 which tends to vary due to the individual difference of the self-adjusting seal 1 does not significantly influence the operation of the self-adjusting seal 1, and hence it is possible to cause the self-adjusting seal 1 to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

In addition, at least one of the low pressure side end surface 26 of the movable seal member 20 and the wall surface 9 of the groove 6 opposing the low pressure side end surface 26 is subjected to the process for facilitating the relative sliding therebetween, whereby variations in the frictional force of the relative sliding portion 29 themselves are reduced, and hence it is possible to cause the self-adjusting seal 1 to operate at desired timing in accordance with the operational state of the rotating turbomachinery.

Although the embodiments of the present invention have been described in detail thus far, the present invention is not limited thereto, and it will be evident that various modifications and changes may be made without departing from the gist of the present invention.

For example, in each of the embodiments described above, although the description has been given of the example in which the relative sliding in the relative sliding portion 29 is facilitated by the single process, the processes for facilitating the relative sliding in the relative sliding portion 29 in the first to third embodiments may be appropriately combined and used.

In addition, in each of the embodiments described above, although the description has been given of the self-adjusting seal 1 in which the stationary seal member 10 and the movable seal member 20 are provided, the seal fins are provided on the inner peripheries of the stationary seal member 10 and the movable seal member 20, and the seal fins and the uneven groove formed along the circumferential direction of the rotor 2 prevent the leakage of the fluid, the self-adjusting seal according to the present invention is not limited to the example. For example, the uneven groove may be provided in the stationary seal member 10 and the movable seal member 20, and the seal fins may be provided on the rotational member (the rotor 2).

FIG. 7 is a cross-sectional view showing an example in which the uneven groove is provided in the movable seal member 20 and the seal fins are provided on the rotor 2. As shown in the drawing, an uneven groove 50 is formed in the inner peripheral surface of the movable seal member 20 opposing the rotor 2 along the circumferential direction, and seal fins 52 are formed on the rotor 2 along the circumferential direction.

Further, as shown in FIG. 7, on the surface of the movable seal member 20 opposing the rotor 2, a coating 54 made of an abradable material is preferably formed by thermal spraying.

With this, even when the movable seal member 20 is brought into contact with the rotor 2 from any cause during the operation of the rotating turbomachinery, the coating 54 is easily cut, and hence it is possible to suppress heat generation, and prevent a bending deformation of the rotational member resulting from the heat generation. On the other hand, the self-adjusting seal 1 having the above-described configuration can operate at desired timing in accordance with the operational state of the rotating turbomachinery, and the seal gap is not reduced before the rotating turbomachinery reaches the rated operation (particularly before passing the critical point during the unsteady operation) in the self-adjusting seal 1, and hence it is possible to prevent the damage beyond expectation resulting from the contact between the coating 54 made of the abradable material and the rotor 2. 

1. A self-adjusting seal for rotating turbomachinery in which a rotational member rotates while confronting a stationary member and energy transfer between the rotational member and a fluid is performed, comprising: a movable seal member fitted in a groove provided in the stationary member along the rotational member; and a biasing member biasing the movable seal member so as to increase a gap between the rotational member and the movable seal member, wherein at least during a rated operation of the rotating turbomachinery, the movable seal member is pressed toward the rotational member against a biasing force of the biasing member by the fluid having flown into an internal portion of the groove via a gap between a high pressure side end surface of the movable seal member and the groove, and at least one of a low pressure side end surface of the movable seal member and a wall surface of the groove opposing the low pressure side end surface is subjected to a process for facilitating relative sliding between the low pressure side end surface of the movable seal member and the wall surface of the groove.
 2. The self-adjusting seal for rotating turbomachinery according to claim 1, wherein, as the process for facilitating the relative sliding, a lubricating coating is formed on at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface.
 3. The self-adjusting seal for rotating turbomachinery according to claim 2, wherein the lubricating coating is formed by application, thermal spraying, or plating.
 4. The self-adjusting seal for rotating turbomachinery according to claim 2, wherein the lubricating coating contains a solid lubricant made of at least one of molybdenum disulfide, graphite, tungsten disulfide, graphite fluoride, boron nitride, copper, nickel, lead, tin, silver, tetrafluoroethylene, polyimide, and high density polyethylene.
 5. The self-adjusting seal for rotating turbomachinery according to claim 4, wherein a dimple for fixing the solid lubricant is formed on at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface.
 6. The self-adjusting seal for rotating turbomachinery according to claim 1, wherein, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member is chamfered.
 7. The self-adjusting seal for rotating turbomachinery according to claim 1, wherein, as the process for facilitating the relative sliding, a surface roughness Ra of at least one of the low pressure side end surface of the movable seal member and the wall surface of the groove opposing the low pressure side end surface is set to not more than 6.3 μm.
 8. The self-adjusting seal for rotating turbomachinery according to claim 1, wherein a coating made of an abradable material is formed on a surface of the movable seal member opposing the rotational member.
 9. The self-adjusting seal for rotating turbomachinery according to claim 2, wherein, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member is chamfered.
 10. The self-adjusting seal for rotating turbomachinery according to claim 3, wherein, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member is chamfered.
 11. The self-adjusting seal for rotating turbomachinery according to claim 4, wherein, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member is chamfered.
 12. The self-adjusting seal for rotating turbomachinery according to claim 5, wherein, as the process for facilitating the relative sliding, a corner of the wall surface of the groove opposing the low pressure side end surface of the movable seal member is chamfered. 